JP2005221951A - Automatic focusing apparatus for camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an automatic focusing apparatus for a camera capable of accurately obtaining a release time lag in a prediction calculation of a moving body and capable of enhancing a moving body predicting performance. <P>SOLUTION: In predicting the release time lag, a mirror driving time at the present temperature is calculated on the basis of the present temperature measuring result and a temperature at a factory adjustment (step S83), the calculated mirror driving time is corrected in accordance with the present camera attitude (step S85). The release time lag is predicted by using the mirror driving time calculated in such the manner (step S88). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an automatic focus adjustment device for a camera, and more particularly to an automatic focus adjustment device for a camera capable of moving object prediction control for focusing on a moving subject.

  There are many techniques related to moving object prediction that perform focus detection and lens drive so that a moving subject is focused. In particular, in a single-lens reflex camera (hereinafter referred to as a camera), in the exposure sequence after an exposure instruction is given by the photographer, the aperture driving and the main mirror driving are simultaneously performed in order to reduce the time lag. That is, in a camera that performs moving object prediction, it corresponds to this defocus amount in order to correct the defocus amount caused by subject movement during the release time lag (the time from the start of exposure by the photographer until the actual exposure starts). The lens is driven during the exposure sequence by the amount of driving lens, that is, the predicted amount of moving object. As a proposal for obtaining such a moving body predicted amount, for example, as disclosed in Patent Document 1, a release time lag is calculated, a defocus amount to be defocused during the release time lag is predicted and calculated, and moving body follow-up driving is performed. is there.

Here, the release time lag used for the moving object prediction calculation is closely related to the driving time of the main mirror of the camera. For example, Patent Document 2 proposes a technique for correcting the release time lag by the driving time of the main mirror and the driving time of the lens. Further, in Patent Document 2, the driving time for driving the main mirror last time is used as the driving time for the main mirror.
Japanese Patent Publication No. 8-30780 JP-A-6-337345

  However, the release time lag cannot always be obtained accurately for the following reason. For example, as in Patent Document 2, when the mirror driving time used when obtaining the release time lag is substituted with the previous measurement result, there is no data at the time of the first photographing. Even if the first mirror drive time is substituted with a predetermined value, it is inaccurate. Most of the release time lag is the drive time of the main mirror, but this drive time also depends on the mechanical parameters of the mirror drive circuit, the camera posture, and the temperature at the time of shooting. Is required. Furthermore, in Patent Document 1 and Patent Document 2, the release time lag is set to the exposure start (that is, the shutter opening start time), but the release time lag used for the moving object prediction calculation is more preferably set to the time half the exposure time. preferable. Therefore, it is preferable to correct the release time lag by the shutter driving time.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an automatic focusing apparatus for a camera capable of accurately obtaining a release time lag in moving object prediction calculation and improving moving object prediction performance.

  In order to achieve the above object, an automatic focusing apparatus for a camera according to a first aspect of the present invention is an automatic focusing apparatus for a camera that performs moving object predictive control for focusing on a moving subject. Drive time prediction means for predicting the drive time of the main mirror of the camera, and release time lag prediction means for predicting a release time lag related to moving object prediction control based on the output of the drive time prediction means .

  According to the first aspect, since the release time lag can be accurately obtained during the moving object prediction control, the moving object prediction performance can be improved.

  ADVANTAGE OF THE INVENTION According to this invention, the automatic focus adjustment apparatus of the camera which can obtain | require a release time lag correctly in a moving body prediction calculation and can improve a moving body prediction performance can be provided.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a conceptual diagram for explaining a main part of an automatic focusing apparatus for a camera according to an embodiment of the present invention. That is, the camera focus control apparatus is provided with a moving object AF control unit 1 that controls the entire moving object AF that performs moving object prediction. The moving object AF control unit 1 includes an exposure time calculation unit as a drive time predicting unit. A unit 2, a temperature measuring unit 3 as a temperature measuring unit, and a posture measuring unit 4 as a posture measuring unit are connected. The exposure time calculation unit 2 calculates the shutter drive time (the time from when the shutter starts to open until the shutter ends) from information such as the brightness of the subject and ISO sensitivity, and inputs the result to the moving object AF control unit 1. To do. The temperature measuring unit 3 measures the temperature inside the camera and inputs the result to the moving object AF control unit 1. Further, the posture measuring unit 4 measures the posture in which the photographer is using the camera and inputs the result to the moving object AF control unit 1.

  Here, the moving object AF control unit 1 includes a release time lag prediction unit 5 as a release time lag prediction unit. The release time lag prediction unit 5 predicts a release time lag used for moving object prediction calculation based on outputs from the exposure time calculation unit 2, the temperature measurement unit 3, and the posture measurement unit 4. The detailed operation of the release time lag prediction unit 5 will be described later. The moving object prediction control unit 1 performs focus control on the moving subject based on the calculation result of the release time lag prediction unit 5. That is, the moving object prediction control unit 1 performs a moving object prediction calculation, which will be described later in detail, based on the calculation result of the release time lag prediction unit 5, and controls the mechatronics control unit 6 based on the result.

  The mechatronic control unit 6 performs mechatronic control such as driving control of the main mirror of the single-lens reflex camera, driving of the aperture in the lens of the single-lens reflex camera, and driving of the focus adjustment lens in the lens of the single-lens reflex camera.

  FIG. 2 is a schematic view of a single-lens reflex camera equipped with an automatic focusing apparatus having the function described in FIG. In other words, this camera includes a camera body 10 and an interchangeable lens unit 11 that can be attached to and detached from the camera body 10. Although this camera is assumed to be a digital still camera, a silver salt camera may be used.

  The interchangeable lens unit 11 includes a focus adjustment lens 12 and a zoom lens 13. The focus adjustment lens 12 is a lens that is driven in the optical axis direction to adjust the focus state of the interchangeable lens unit 11. The zoom lens 13 is a lens that is driven in the optical axis direction to change the focal length of the interchangeable lens unit 11.

  On the other hand, the camera body 10 includes a main mirror 14, a sub mirror 15, a focus detection optical system 16, a focus detection sensor (hereinafter referred to as AF sensor) 17, a focal plane shutter 18, an image sensor 19, a screen mat 20, and a viewfinder optical system 21. And an eyepiece lens 22.

  The main mirror 14 is composed of a half mirror, which partially transmits and partially reflects the light flux from the subject. Here, the main mirror 14 is configured to be rotatable in a direction indicated by an arrow in the drawing so that all light fluxes go to an image pickup surface constituted by the image pickup element 19 at the time of exposure.

  On the other hand, the light beam from the subject that has passed through the main mirror 14 is reflected by the sub mirror 15 and guided to the focus detection optical system 16 except during exposure. The focus detection optical system 16 includes a lens for focus detection and the like, and guides the light beam reflected by the sub mirror 15 to the AF sensor 17. The detailed configuration of the focus detection optical system 16 will be described in detail later. The AF sensor 17 is, for example, a sensor composed of a photodiode array. The AF sensor 17 is configured to be able to detect a plurality of focal points. That is, the AF sensor 17 has a plurality of photodiode arrays corresponding to a plurality of focus detection areas. The detailed configuration of the AF sensor 17 will be described in detail later.

  As described above, at the time of exposure, the main mirror 14 is retracted from the optical axis of the interchangeable lens unit 11, so that the light flux from the subject is incident in the imaging surface direction. At this time, the focal plane shutter 18 is driven and controlled to give an appropriate amount of light to the imaging surface. Here, in the case of a digital still camera, a CCD is used as the image pickup device 19 constituting the image pickup surface. In the case of a silver salt camera, a silver salt film is used instead of the image sensor 19. When the above-described focal plane shutter 18 is opened, the light flux from the subject is incident on the imaging surface formed by the imaging device 19.

  At times other than exposure, the light beam from the subject reflected by the main mirror 14 is incident in the finder direction and an image is formed by the screen mat 20. This image enters the eyepiece 22 via the finder optical system 21. The photographer can know the photographing range and the focus state of the subject by looking into the eyepiece 22.

  FIG. 3 is a schematic diagram of the focus detection area displayed in the viewfinder. The example of FIG. 3 is an example of multi-AF having three distance measuring areas. That is, when the photographer looks into the eyepiece 22, the focus detection area mark corresponding to the plurality of focus detection areas of the AF sensor 17, that is, the center distance measurement area mark 25 and the right distance measurement area mark are displayed in the finder. 26 and the left distance measuring area mark 27 are displayed.

Next, an electrical configuration relating to such a camera will be described with reference to FIG.
First, the structure regarding the interchangeable lens part 11 is demonstrated. A zoom drive rotary ring 51 and a manual focus (MF) rotary ring 58 that are ring-shaped so as to surround the periphery of the interchangeable lens unit 11 are formed outside the interchangeable lens unit 11. The photographer can change the focal length of the interchangeable lens unit 11 by driving the zoom lens 13 in the optical axis direction by rotating the zoom driving rotary ring 51 about the optical axis of the interchangeable lens unit 11. .

  Further, when the MF rotating ring 58 is rotated about the optical axis of the interchangeable lens unit 11, the focus adjustment lens 12 is driven in the optical axis direction in conjunction with the rotation. Thereby, the focus of the interchangeable lens part 11 can be adjusted manually. The MF rotating ring 58 is used when the photographer selects a manual focus mode by operating a changeover switch (not shown) that switches between an autofocus mode and a manual focus mode.

  The inside of the interchangeable lens unit 11 is an in-lens CPU (hereinafter, referred to as a lens adjustment control, a diaphragm drive control, a communication control, etc.) for the focus adjustment lens 12, the zoom lens 13, the diaphragm 53, and the interchangeable lens unit 11. , Referred to as LCPU). The LCPU 50 is connected to a zoom position detection circuit 52, a diaphragm drive circuit 54, a lens drive circuit 55, a lens position detection circuit 56, and a communication circuit 57.

  The position of the zoom lens 13 driven by the zoom driving rotary ring 51 is detected by a zoom position detection circuit 52. The LCPU 50 obtains focal length information of the interchangeable lens unit 11 based on the position of the zoom lens 13 detected by the zoom position detection circuit 52.

  The diaphragm 53 is configured to include an opening for adjusting the amount of light incident in the direction of the camera body 10. The LCPU 50 controls the diaphragm drive circuit 54 to change the size of the opening of the diaphragm 53 so that an appropriate amount of light enters the camera body 10 direction.

  In the autofocus mode, the LCPU 50 controls the lens driving circuit 55 to drive the focus adjustment lens 12. The lens position detection circuit 56 detects the position of the focus adjustment lens 12 driven by the lens driving circuit 55. Here, the lens position detection circuit 56 includes, for example, a photo interrupter (PI) circuit. The photo interrupter circuit is a circuit that detects the amount of rotation of the driving motor of the lens driving circuit 55 by converting it into the number of pulses. That is, the lens position detection circuit 56 detects the absolute position from the focus adjustment lens 12 as the number of pulses from a certain reference position. The LCPU 50 can calculate the focus state information of the interchangeable lens unit 11 based on the lens position detected by the lens position detection circuit 56.

  Further, the LCPU 50 communicates information such as the aperture driving amount and the defocus amount of the interchangeable lens unit 11 with the CPU and AF / AECPU of the camera body, which will be described in detail later, via the communication circuit 57. For this reason, the communication connection terminal of the communication circuit 57 is provided outside the interchangeable lens unit 11.

  Next, a configuration related to the camera body 10 will be described. That is, a main body CPU 59 that controls the entire camera is provided inside the camera body 10. The main body CPU 59 temporarily stores a communication line 60 for communicating with the LCPU 50 via the communication circuit 57, a flash ROM (FROM) 61 in which a program of the main body CPU 59 is stored, and various types of information of the main body CPU 59. A RAM 62, an image sensor control circuit 63 that controls the image sensor 19 to obtain image data, a strobe control circuit 64 that controls a strobe (not shown), a mirror control circuit 65 that controls the up and down of the main mirror 14, and a focal plane shutter 18 are provided. A shutter control circuit 66 for controlling, an image processing circuit 67 for image processing of image data obtained by the image sensor control circuit 63, a display circuit 68 for displaying a photographed image and various photographing information on a display unit (not shown), a photographer Operation switch circuit connected to various operation switches operated by 9. A power supply circuit 72 for supplying power to the camera, a temperature measurement circuit 82 for measuring the temperature inside the camera, an attitude measurement circuit 83 for measuring the attitude of the camera, and an AF / AECPU 74 are connected. .

  Here, the operation switch circuit 69 includes a change-over switch (not shown) that switches the shooting mode of the camera, a release switch that operates by operating a release button, and the like. Here, the release switch in the present embodiment is a general two-stage switch. That is, when the release button is half-pressed, the first release switch 70 (hereinafter referred to as 1R switch) is turned on to perform focus detection and photometry, and the focus adjustment lens 12 is driven to be in focus. Further, when the release button is fully pressed, the second release switch 71 (hereinafter referred to as a 2R switch) is turned on, and the main mirror 14 and the focal plane shutter 18 are driven to start exposure.

  The power supply circuit 72 is a circuit that smoothes or boosts the voltage of the loaded battery 73. The temperature measurement circuit 82 is a circuit that measures the temperature inside the camera body 10, particularly around the main mirror 14, and includes a temperature detection element such as a thermistor. The posture measurement circuit 83 is a circuit for measuring the posture (front, upward, downward, etc.) of the camera when the photographer holds the camera, and includes a known posture sensor.

  The AF / AECPU 74 performs automatic focus adjustment (AF) control and photometry (AE) control of the camera. Here, the AF / AECPU 74 has the function of the moving object prediction control unit 1 of FIG. The AF / AECPU 74 includes a communication line 75 for communication between the AF / AECPU 74 and the communication circuit 57 of the interchangeable lens unit 11, a communication line 76 for communication between the AF / AECPU 74 and the main body CPU 59, and the AF / AECPU 74. Are connected to a flash ROM (FROM) 77 in which are stored, a RAM 78 for temporarily storing various information of the AF / AECPU 74, a photometry circuit 79, a focus detection circuit 80, and an auxiliary light circuit 81.

  Here, the photometric circuit 79 is a circuit for obtaining subject luminance information by controlling a photometric element (not shown) that measures the subject luminance. The exposure time is calculated based on the subject luminance information obtained by the photometry circuit 79. The focus detection circuit 80 is a circuit for performing focus detection calculation based on information obtained by controlling the AF sensor 17 and obtaining focus detection information. Further, the auxiliary light circuit 81 uses a light emitting element such as an LED to emit auxiliary light when the focus detection by the focus detection circuit 80 is impossible because the subject has low brightness and focus detection needs to be performed again. It is a circuit for irradiating.

Next, the configuration of the focus detection optical system 16 and the AF sensor 17 will be described in detail with reference to FIG.
In FIG. 5, the field mask 41 narrows the light beam obtained through the sub mirror 15. The field mask 41 has three openings 41a, 41b, and 41c in order to transmit the light beams (indicated by a one-dot chain line in the figure) of the three focus detection regions guided from the sub mirror 15.

  The infrared cut filter 42 is a filter for cutting an infrared light component harmful to focus detection. The condenser lens 43 is for collecting the light that has passed through the infrared cut filter 42. Here, the condenser lens 43 includes three condenser lenses 43a, 43b, and 43c that are arranged corresponding to the positions of the three openings 41a, 41b, and 41c, respectively.

  The total reflection mirror 44 reflects the light beam incident through each condenser lens in the direction of the separator diaphragm mask 45. The separator diaphragm mask 45 is for narrowing the incident light flux. Here, the separator aperture mask 45 divides the light beams of the three focus detection regions obtained through the condenser lenses 43a, 43b, and 43c into two light beams, respectively, so as to respectively separate the three focus detection regions. It has three provided openings 45a, 45b, 45c.

  The separator lens 46 re-images the light beam obtained through the separator diaphragm mask 45 described above. Here, the separator lens 46 includes three separator lenses 46a, 46b, and 46c provided for the three focus detection areas, respectively.

  The AF sensor 17 includes a photodiode array 47 that is a photoelectric conversion element array that obtains a light intensity signal corresponding to the light intensity distribution of the received light flux. Here, the photodiode array 47 includes three photodiode arrays 47a, 47b, and 47c provided for the light beams in the three focus detection regions. That is, the two light beams divided by the separator lenses 46a, 46b, and 46c are incident on the corresponding photodiode arrays 47a, 47b, and 47c to form an image. Here, the photodiode array 47a is arranged in a direction corresponding to the horizontal direction of the shooting screen, and the other two photodiode arrays 47b and 47c are respectively positioned in positions not including the optical axis in the vertical direction of the shooting screen. Arranged in the corresponding direction.

  Here, the photographing lens 48 shown in FIG. 5 is a virtual lens obtained by synthesizing each lens group in the interchangeable lens unit 11, for example, the focus adjustment lens 12 and the zoom lens 13 described above. In the focus detection optical system 16 configured as shown in FIG. 5, focus detection light beams that pass through different regions 48a and 48b and regions 48c and 48d on the exit pupil plane of the photographing lens 48 are converted into photodiode arrays 47a, 47b, Each light is received by 47c and converted into an electric signal (light intensity signal) indicating a light intensity distribution pattern of the image. This light intensity signal is used when AF calculation is performed using a TTL phase difference method which is one method of focus detection.

  FIG. 6 is a flowchart of a subroutine for explaining the AF calculation executed in the continuous AF mode of such a camera.

  In the single-lens reflex camera equipped with the automatic focusing device according to the present embodiment, an AF mode changeover switch (not shown) included in the operation switch circuit 69 is used to switch between the single AF mode and the continuous AF mode. Switching is possible. Here, the single AF mode is an AF mode in which the focus is locked once an in-focus state is detected, and the continuous AF mode is used to focus on a moving subject by continuously performing focus detection and lens driving. This is an AF mode for performing so-called moving object prediction AF. FIG. 6 is a flowchart of an AF calculation subroutine executed during the continuous AF.

  The AF / AECPU 74 starts the operation of a predetermined timer for measuring the integration time interval (step S10). The integration interval measured by this timer is stored in a predetermined memory (here, RAM 78). Here, in the continuous AF mode, since the integration is repeatedly performed, the AF / AECPU 74 starts the timer operation in synchronization with the start of the integration operation even after the start of the first timer operation.

  Next, the integration operation of the AF sensor 17 is controlled (step S11). Further, a gain for reading sensor data detected by the AF sensor 17 is set (step S12). Thereafter, the sensor data detected by the AF sensor 17 is read and stored in the RAM 78 (step S13).

  Next, the AF / AECPU 74 causes the focus detection circuit 80 to perform a predetermined correlation calculation (step S14). This correlation calculation is a calculation for calculating the correlation amount of two images on the photodiode arrays 47a, 47b, 47c divided by the separator lenses 46a, 46b, 46c based on the sensor data detected by the AF sensor 17. From the correlation calculation result, the AF / AECPU 74 performs a reliability determination process for determining whether or not the data detected by the AF sensor 17 is reliable, that is, whether or not AF is possible (step S15). The reliability determination result is stored in the RAM 78.

  Next, the AF / AECPU 74 determines the result of the reliability determination process (step S16). In step S16, if it is determined that there is no reliability as a result of the reliability determination process in step S15, it is determined whether it is determined that there is no reliability continuously for a predetermined number of times (step S17). ). If it is determined in step S17 that there is no reliability continuously for a predetermined number of times, the process proceeds to step S12 and recalculation is performed using the data of the distance measuring point next to the current distance measuring point. To start. On the other hand, as a result of the determination in step S17, if it is not yet determined that there is no reliability for a predetermined number of times, the process returns to step S10 in order to continue detection at the current distance measuring point. That is, the detection at the current distance measuring point is continued until a predetermined number of times, and when the reliability is low a predetermined number of times, the distance measuring point is given up and the calculation is performed at the adjacent distance measuring point.

  On the other hand, if it is determined in step S16 that the reliability is determined as a result of the reliability determination process, the AF / AECPU 74 causes the focus detection circuit 80 to detect the photographic lens 48 based on the correlation amount calculated in step S14. Is calculated (step S18). The calculated defocus amount is stored in the RAM 78 and simultaneously transmitted to the LCPU 50. Subsequently, a continuity determination process for comparing the previously detected defocus amount with the currently detected defocus amount is performed (step S19). Here, “continuity” is a term indicating that the subject exists at the same distance measuring point as the previous time. A flowchart of this continuity determination process is shown in FIG.

  That is, in the continuity determination process, first, the absolute value of the difference between the absolute value of the previous defocus amount and the absolute value of the current defocus amount is calculated (step S30). Here, the absolute value of this difference is defined as the continuity coefficient. Next, it is determined whether or not the continuity coefficient is smaller than a predetermined value (step S31). When it is determined that the continuity coefficient is smaller than a predetermined value, that is, when the difference between the previous defocus amount and the current defocus amount is small to some extent, it is determined that the continuity is continuous and a predetermined flag indicating that the continuity coefficient is continuous is set. (Step S32). On the other hand, if it is determined in step S31 that the continuity coefficient is greater than or equal to a predetermined value, that is, if the difference between the previous and current defocus amounts is large, it is determined that the discontinuity is discontinuous. Is set (step S33). After the above operation, the continuity determination process is terminated.

  Here, it returns to the flowchart of FIG. 6 again. After the continuity determination process, the AF / AECPU 74 determines whether or not a predetermined flag indicating continuity is set (step S20). If it is determined in step S20 that it is continuous, the AF calculation of this flowchart ends.

  On the other hand, as a result of the determination in step S20, if it is determined that the distance is discontinuous, it is determined whether or not the distance measurement points (three points) are discontinuous (step S21). If it is determined in step S21 that one of the distance measuring points is continuous, the process proceeds to step S12, and AF calculation is performed at the distance measuring point having the continuity.

  On the other hand, if it is determined in step S21 that all the distance measuring points are discontinuous, it is determined whether or not the AF calculation at the previous distance measuring point is reliable (step S22). If it is determined that the AF calculation at the previous distance measurement point is reliable, the previously selected distance measurement point is selected (step S23), and then the AF calculation of this flowchart ends. On the other hand, as a result of the determination in step S22, when it is determined that the AF calculation at the previously selected distance measurement point is not reliable, the distance measurement point with the smallest defocus amount among the current three distance measurement points. After selecting (step S24), the AF calculation of this flowchart is terminated. That is, in the selection of the distance measurement points, the distance measurement points that are considered to have the most continuity are selected.

  FIG. 8 is a timing chart before and after the 2R switch 71 is turned on during continuous AF.

  First, a sequence when the 1R switch 70 is in an on state and the 2R switch 71 is in an off state (hereinafter referred to as a 1R sequence) will be described. First, as a result of the first AF calculation, the LCPU 50 calculates the lens driving amount based on the transmitted defocus amount. Here, this lens driving amount corresponds to the number of driving pulses of the lens driving circuit 55. Thereafter, the lens driving circuit 55 starts driving the focus adjustment lens 12 based on the calculated number of driving pulses.

  The AF / AECPU 74 performs the next AF calculation immediately after the AF calculation is completed and the defocus amount is transmitted to the LCPU 50. That is, the AF / AECPU 74 performs AF calculation in parallel with the LCPU 50 driving the lens. Each time the AF calculation is completed, the calculated defocus amount is transmitted to the LCPU 50.

  The LCPU 50 calculates the lens driving amount based on the defocus amount transmitted from the AF / AECPU 74 in parallel with causing the lens driving circuit to drive the lens. Then, a drive target position is calculated from the calculated lens drive amount, and the data is returned to the AF / AECPU 74. Thereafter, these operations are repeated. Here, the drive target position will be described later.

  When the first lens drive is completed, the LCPU 50 transmits a lens drive end signal to the AF / AECPU 74. When the AF / AECPU 74 receives the lens drive end signal, the AF / AECPU 74 causes the photometric circuit 79 to perform a photometric operation after the currently calculated AF calculation.

  As described above, when the 1R switch 70 is on and the 2R switch 71 is off, the AF, AE, and lens driving operations are repeated. Further, as described with reference to FIG. 6, the AF / AECPU 74 stores information such as the AF interval (that is, the integration time counted by the timer) and the defocus amount in a predetermined memory, in this case, the RAM 78.

  Next, a sequence in a state where the 2R switch 71 is turned on (hereinafter referred to as a 2R sequence) will be described. Here, the 2R switch 71 is a switch that the photographer turns on at an arbitrary timing. That is, the 2R switch is turned on at any timing in the 1R sequence. Here, a case will be described in which the 2R switch 71 is turned on when the AF / AECPU 74 is performing an AF calculation and the LCPU 50 is driving a lens.

  Since the 2R switch 71 is turned on, the camera shifts to an exposure operation. That is, in the LCPU 50, the previous lens driving is continued, but the AF / AECPU 74 stops the currently calculated AF calculation and performs the moving object prediction calculation in order to reduce the time lag. This moving object prediction calculation will be described in detail later.

  Then, the amount of movement of the subject during the release time lag (the time from when the 2R switch 71 is turned on until the exposure operation is started) is predicted by the moving body prediction calculation, and the lens driving amount is calculated from the predicted amount. Calculate. Further, the final target position of the focus adjustment lens 12 is obtained from the predicted drive amount, and the obtained final drive position information is transmitted to the LCPU 50. These operations will be described in detail later.

  The LCPU 50 further drives the lens to the received drive target position. In other words, since the lens drive is continued at the previous lens drive amount, the lens drive is continued to the updated target position. Further, the LCPU 50 receives the predicted driving amount from the AF / AECPU 74 and simultaneously receives the driving amount of the diaphragm 53. Here, the aperture driving amount is a result calculated by the photometric circuit 79 based on the latest photometric result. Further, the LCPU 50 drives the diaphragm 53 by controlling the diaphragm drive circuit 54 based on the received diaphragm drive amount. That is, during the lens driving, the diaphragm 53 is also driven simultaneously.

  On the other hand, the main body CPU 59 drives the main mirror 14 to the up position by the mirror control circuit 65. That is, when the LCPU 50 performs lens driving and diaphragm driving, mirror driving is also performed in parallel by the main body CPU 59. The reason why the three mechatronic controls are performed in parallel is to reduce the time lag.

  Further, the main body CPU 59 drives the focal plane shutter 18 via the shutter control circuit 66 when all of these three mechatronic controls are completed. At this time, an image is captured by the image sensor 19. Here, the driving time of the focal plane shutter 18 is a time calculated based on the photometric result of the photometric circuit 79.

  Finally, the main body CPU 59 controls the image sensor 19 by the image sensor control circuit 63 to obtain image data. The image data obtained in this way is stored in the RAM 62.

  FIG. 9 is a flowchart of the 2R sequence described in FIG. Note that the 2R sequence processing is continued from the 1R sequence, and therefore it is assumed that the lens drive is continued.

  Since the 2R switch 71 is turned on, the AF / AECPU 74 stops the currently calculated AF calculation (in some cases, AE calculation) in order to shorten the time lag (step S40). Next, a moving object prediction calculation is performed (step S41), and the amount that the subject will move during the release time lag is predicted. This moving object prediction calculation will be described in detail later. Next, the obtained prediction result is transmitted to the LCPU 50 (step S42), and at the same time, the driving amount of the diaphragm 53 is also transmitted to the LCPU 50 (step S43). The aperture driving amount is a result calculated by the photometry circuit 79 based on the latest photometry result.

  Next, the main body CPU 59 controls the mirror control circuit 65 to drive the main mirror 14 to the up position (step S44). Next, the LCPU 50 controls the diaphragm drive circuit 54 based on the received diaphragm drive amount to drive the diaphragm 53 (step S45). At this time, the LCPU 50 is still driving the lens. That is, the lens driving continued from the 1R sequence is performed until the focus adjustment lens 12 reaches the final target position corrected in step S42. When the diaphragm drive and the lens drive are completed, the LCPU 50 transmits a message to that effect to the main body CPU 59 (step S46). Further, the main body CPU 59 determines whether or not a drive end signal has been received (step S47). If it is determined in step S47 that the drive end signal has not been received, the process waits until the drive signal is received.

  On the other hand, if it is determined in step S47 that the drive end signal has been received, the main body CPU 59 controls the shutter control circuit 66 to drive the focal plane shutter 18. Thereby, an image is picked up by the image pickup device 19. Here, the shutter driving time at this time is a time calculated by the photometry circuit 79. Then, the main body CPU 59 controls the image sensor 19 with the image sensor control circuit 63 to obtain image data (step 48). Next, the image data obtained in this way is stored in the RAM 62 (step S49).

  Next, the concept of moving object prediction will be described with reference to FIG. Here, the focus adjustment lens 12 is configured to move on the optical axis when a driving cam (not shown) is rotated by driving of the lens driving circuit 55. A curve 100 indicates the position of the cam in the optical axis direction with respect to the rotation amount of the drive cam. The horizontal axis in FIG. 10 represents the rotation amount of the drive cam, but also the number of pulses measured from a certain reference position by a photo interrupter (not shown) of the lens position detection circuit 56. Further, the vertical axis in FIG. 10 represents the lift amount of the drive cam when it is rotated by a predetermined amount from a certain reference position.

  As described above, the defocus amount detected in the 1R sequence is transmitted to the LCPU 50, and the number of pulses calculated by the LCPU 50 is returned to the AF / AECPU 74. At this time, when the calculated number of pulses is added to the current position on the drive cam of the focus adjustment lens at the start of integration, it is the in-focus position of the subject at the start of integration (hereinafter referred to as the drive target position. Are indicated by reference numerals 101 to 106). The drive target position is transmitted to the AF / AECPU 74, and the AF / AECPU 74 stores the information in a predetermined RAM 78. The RAM 78 also stores time intervals for each AF, reliability information for each AF, and the like.

  When the 2R switch 71 is turned on, the AF / AECPU 74 performs a moving object prediction calculation and predicts the drive target position after the release time lag. Then, the shutter driving is performed through the 2R sequence as described above.

  FIG. 11 is a flowchart of the moving object prediction calculation in step S41 of FIG. That is, in the moving object prediction calculation, first, a plurality of distance measurement results (for example, three points) are selected from a plurality of past distance measurement results (that is, drive target positions 101 to 106) (step S70). As a selection criterion for this distance measurement result, the latest distance measurement result is prioritized, and furthermore, highly reliable data based on the reliability information stored in the RAM 78 is employed. Next, a release time lag is predicted (step S71). For example, in the example described with reference to FIG. 10, the mirror driving time and the exposure time (that is, the shutter driving time) are the release time lag. The method for predicting the release time lag will be described in detail later.

  After predicting the release time lag, a coefficient of a prediction formula for predicting the drive amount after the release time lag is calculated (step S72). Here, the prediction formula is, for example, a quadratic formula, and the coefficient varies depending on the release time lag and the distance measurement time interval selected in step S70 (previously stored in the RAM 78), and is calculated each time. Thereafter, the drive amount after the release time lag is predicted based on the determined prediction formula (step S73). This prediction result is the final target position of the focus adjustment lens 12, and is transmitted to the LCPU 50 in step S42 in FIG.

  Next, the release time lag prediction in step S71 of FIG. 11 will be described. FIG. 12 is a diagram showing the relationship between the temperature inside the camera, particularly in the vicinity of the main mirror 14, and the mirror driving time when the photographer holds the camera in the front, that is, the so-called normal position. More specifically, the mirror drive time is the mirror up drive time from when the main mirror 14 starts to rise until the rise is completed. As shown in FIG. 12, the mirror driving time becomes shorter as the temperature becomes higher, and the mirror driving time becomes longer as the temperature becomes lower. Here, since the relationship between the camera internal temperature and the mirror driving time varies for each camera, an example of typical three cameras ABC (maximum mirror driving time, average, minimum) is shown here. Show. Such variations among cameras are caused by, for example, the mechanical performance of the main mirror 14, the performance of a motor (not shown) in the mirror control circuit 65, and the performance of a motor drive circuit (not shown) in the mirror control circuit 65. Is for etc. That is, since the relationship between the camera internal temperature and the mirror drive time varies from camera to camera, it is necessary to adjust the mirror drive time for each camera in the camera assembly process.

  FIG. 13 is a diagram showing the relationship between the camera posture and the mirror drive time at room temperature (about 25 ° C.). As shown in FIG. 13, the rate of change in the mirror drive time relative to the change in the camera attitude is smaller than the rate of change in the mirror drive time relative to the change in the camera temperature, and adjustment is almost necessary depending on the mechanical performance. There is no level. Here, FIG. 13 also shows an example of typical three cameras ABC (maximum, average, and minimum of the mirror driving time, respectively) in consideration of the variation for each camera. Note that such a variation from camera to camera occurs because the amount of mechanical load on the main mirror 14 changes depending on the posture of the camera.

  FIG. 14 is a diagram showing the concept of the release time lag. As described with reference to FIG. 8, at the timing when the 2R switch 71 is turned on, the AF operation being executed at that time is stopped halfway in order to shorten the release time lag. Here, the defocus amount used for the moving object prediction calculation is based on the latest AF data (that is, the defocus amount) that has been calculated at that time and the latest AF data as a reference, and then has high reliability. AF data is used.

  That is, lens driving is controlled based on past AF data. Here, since new AF data is obtained every time the AF described with reference to FIG. 6 is performed, the lens driving is performed while updating the lens driving target position accordingly. The AF interval used for the moving object prediction calculation at this time is an interval based on a time point that is half the integration time in each AF. The AF interval is measured by a timer (not shown) in the AF / AECPU 74.

  When the 2R switch 71 is turned on, the moving object prediction described with reference to FIG. 11 is performed. At this time, the time from the half of the integration time in AF stopped at the timing when the 2R switch 71 is turned on to the start of moving object prediction calculation is measured by a predetermined timer in the AF / AECPU 74. Further, the time from the start of the moving object prediction calculation until the actual driving of the main mirror 14 is also measured in the same manner. Here, since there is almost no variation in the time from the start of the moving object prediction calculation to the actual driving of the main mirror 14, even a fixed value can be substituted. After the drive of the main mirror 14 has started and the mirror drive time has elapsed, the focal plane shutter 18 is opened for the shutter drive time calculated by the AF / AECPU 74 based on the subject brightness measured by the photometry circuit 79. And it leads to exposure.

  At this time, the release time lag felt by the photographer is the time from the timing when the 2R switch 71 is turned on until the opening of the focal plane shutter 18 (or the opening end). However, the total release time lag in the moving object prediction calculation is from the time half of the integration time in the latest AF used for the moving object prediction calculation to the time half of the drive time of the focal plane shutter 18. Here, the reason for setting the release time lag not to the time of opening of the focal plane shutter 18 but to the time of half of the driving time of the focal plane shutter 18 is from the start of exposure (start of shutter opening) to the end of exposure (shutter opening). This is to average the amount of movement of the subject until (end).

  From the above, as shown in FIG. 14, the total release time lag in the moving object prediction calculation is the total release time lag in the moving object prediction calculation = AF interval a (the 2R switch from the half of the integration time in the latest AF). (Time until the time of half of the integration time in AF when 71 is turned on) + time to start moving object prediction + time to start mirror driving + mirror driving time + (shutter driving time / 2).

  FIG. 15 is a block diagram showing the concept of mirror drive time calculation. As described with reference to FIG. 14, the total release time lag in the moving object prediction calculation includes the mirror driving time, and calculating this mirror driving time accurately is indispensable for improving the moving object prediction accuracy. is there.

  The mirror drive time calculation unit 200 is provided in the AF / AECPU 74, and calculates the drive time of the main mirror 14 based on the factory adjustment time data 201, the current temperature information 204, and the current attitude information 205. Here, the factory adjustment time data 201 is data stored in the FROM 61 at the time of camera adjustment in a factory or the like, and includes temperature data 202 at the time of factory adjustment and mirror drive time data 203 at the time of factory adjustment. The current temperature information 204 is the current temperature inside the camera (particularly the temperature around the main mirror) measured by the temperature measurement circuit 82, and the current temperature information 204 is the current camera measured by the attitude measurement circuit 83. It is posture.

  Hereinafter, details of the mirror drive time calculation under a predetermined condition, that is, a predetermined temperature and a predetermined camera posture will be described. FIG. 16 is a flowchart of a release time lag prediction calculation subroutine in step S71 of FIG.

  That is, the mirror drive time calculation unit 200 in the AF / AECPU 74 reads the current temperature inside the camera, which is the output of the temperature measurement circuit 82 (step S80). Next, the mirror drive time calculation unit 200 reads temperature data at the time of factory adjustment stored in the FROM 61 (step S81).

  Next, the mirror drive time calculation unit 200 reads the mirror drive time data at the time of factory adjustment stored in the FROM 61 (step S82). The mirror drive time data at the time of factory adjustment is measured by driving the main mirror 14 once at the time of adjustment in a factory or the like. That is, the mirror drive time data is measured by driving the main mirror 14 with the camera held in the normal position during factory adjustment. This measurement may be performed by storing a subroutine program for adjustment in the FROM 77 so that it can be measured by a timer in the AF / AECPU 74, for example. Here, the mirror drive time data at the time of factory adjustment is stored in the FROM 61 in order to absorb individual differences for each camera as described with reference to FIG.

  After reading the mirror drive time data at the time of factory adjustment, the mirror drive time calculation unit 200 calculates the mirror drive time when the camera is in the normal position under the current environment (step S83). This can be obtained by mirror drive time at the normal position = mirror drive time at factory adjustment + (temperature at factory adjustment−current temperature) × coefficient. Here, the coefficient in the equation can be obtained from the characteristics shown in FIG. Alternatively, the relationship between each temperature in FIG. 12 and the mirror driving time can also be obtained by storing the relationship in the FROM 61 as a table.

  Next, the mirror drive time calculation unit 200 reads the current camera posture, which is the output of the posture measurement circuit 83 (step S84). Then, the mirror drive time calculation unit 200 corrects the mirror drive time at the normal position calculated in step S83 based on the relationship between the camera posture and the mirror drive time as described in FIG. 13 (step S85). As described with reference to FIG. 13, when the change in the mirror driving time due to the camera posture difference is small, the influence of the posture difference can be ignored. In this case, the processing in step S84 and step S85 may be omitted.

  Next, the AF / AECPU 74 reads the AF interval a described with reference to FIG. 14 (step S86). Further, the AF / AECPU 74 obtains the time until the moving object prediction described with reference to FIG. 14 (step S87).

  From each time obtained above, the AF / AECPU 74 obtains a total release time lag for moving object prediction (step S88). The release time lag obtained in this way is used for the moving object prediction calculation in step S72 and step S73 of FIG. If the influence of temperature change of the mirror driving time is not considered, the mirror driving time may be a fixed value determined only by the mechanical parameters of the mirror control circuit 65. In this case, the processing from step S80 to step S83 can also be omitted.

  As described above, according to the present embodiment, it is possible to calculate an accurate mirror driving time in consideration of at least one of the current temperature and the current camera posture, so that the total release time lag in the moving object prediction calculation can be calculated. It can be done accurately. Therefore, improvement of moving object prediction accuracy can be expected.

  Although the present invention has been described based on the above embodiments, the present invention is not limited to the above-described embodiments, and various modifications and applications are naturally possible within the scope of the gist of the present invention.

  Further, the above-described embodiments include various stages of the invention, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements. For example, even if some constituent requirements are deleted from all the constituent requirements shown in the embodiment, the problem described in the column of the problem to be solved by the invention can be solved, and the effect described in the column of the effect of the invention Can be extracted as an invention.

It is a conceptual diagram for demonstrating the principal part of the automatic focus adjustment apparatus of the camera which concerns on one Embodiment of this invention. It is a general-view figure of the single-lens reflex camera carrying the automatic focus adjustment apparatus which concerns on one Embodiment of this invention. It is the schematic about the focus detection area displayed in a finder. It is a block diagram for demonstrating the electrical structure regarding the camera used in one Embodiment of this invention. It is a disassembled perspective view for demonstrating in detail the structure of a focus detection optical system and AF sensor. It is a flowchart of AF calculation processing executed at the time of continuous AF. It is a flowchart of a continuity determination process. 6 is a timing chart before and after the 2R switch is turned on during continuous AF. It is a flowchart which shows the control procedure in a 2nd release sequence. It is a conceptual diagram of a moving body prediction. It is a flowchart in a moving body prediction calculation. It is a figure which shows the relationship between the temperature inside a camera, and the mirror drive time when holding a camera in a normal position. It is a figure which shows the relationship between the attitude | position of a camera, and the mirror drive time at normal temperature. It is the figure shown about the concept of release time lag. It is a block diagram shown about the concept of mirror drive time calculation. It is a flowchart of a subroutine of a release time lag prediction calculation.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Moving body prediction control part, 2 ... Exposure time calculating part, 3 ... Temperature measurement part, 4 ... Attitude measurement part, 5 ... Release time lag prediction part, 6 ... Mechatronics control part, 50 ... In-lens CPU (LCPU), 51 ... Rotating ring for zoom drive, 52 ... Zoom position detection circuit, 53 ... Aperture, 54 ... Aperture drive circuit, 55 ... Lens drive circuit, 56 ... Lens position detection circuit, 57 ... Communication circuit, 58 ... Rotation for manual focus (MF) Ring 59, main body CPU, 60, 75, 76 ... communication line 61, 77 ... flash ROM (FROM), 62, 78 ... RAM, 63 ... image sensor control circuit, 64 ... strobe control circuit, 65 ... mirror control circuit , 66 ... shutter control circuit, 67 ... image processing circuit, 68 ... display circuit, 69 ... operation switch circuit, 70 ... first release switch (1R switch), 71 ... second Leeds switch (2R switch), 72 ... power supply circuit, 73 ... battery, 74 ... AF / AECPU, 79 ... photometry circuit, 80 ... focus detection circuit, 81 ... auxiliary light circuit, 82 ... temperature measurement circuit, 83 ... attitude measurement circuit , 200 ... mirror driving time calculation unit, 201 ... factory adjustment data, 202 ... temperature data, 204 ... current temperature information, 205 ... current posture information

Claims (4)

In an automatic focus adjustment device of a camera that performs moving object prediction control for focusing on a moving subject,
Drive time prediction means for predicting the drive time of the main mirror of the camera under a predetermined condition;
A release time lag predicting means for predicting a release time lag related to moving object predictive control based on the output of the drive time predicting means;
An automatic focusing apparatus for a camera, comprising: A temperature measuring means for measuring the temperature inside the camera;
2. The automatic focusing apparatus for a camera according to claim 1, wherein the driving time predicting unit predicts the driving time of the main mirror based on the temperature inside the camera measured by the temperature measuring unit. It further comprises posture measuring means for measuring the posture of the camera,
3. The automatic focusing apparatus for a camera according to claim 1, wherein the driving time predicting unit predicts the driving time of the main mirror based on the posture of the camera measured by the posture measuring unit.   4. The camera according to claim 1, wherein the release time lag predicting unit predicts the driving time of the main mirror further considering a time half of the shutter driving time of the camera. Automatic focusing device.

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